Rubber heel and method of making the same



Dec. 249 1929. w. B. wwsco'r's 1,740,633

RUBBER HEEL AND METHOD OF MAKING THE SAME y Filed March 28, 1924 Patented Dec. 24, 1929 UNITED STATES WILLIAM BURTON WESCOTT, OF DOVER,

MASSACHUSETTS, ASSIGNOR TO RUBBER LATEX RESEARCH CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS RUBBER HEEL AND METHOD 0F MAKING THE SAME Application ledllarch 28, 1924. Serial No. 702,549.

The present invention relates toan improvement in rubber heels and method of making the same.

The object of the invention is to produce a rubber heel light in weight, highly resilient,

fibre. In other cases textile fibre has been incorporated into the rubber compound in the rubber mill. .In this case the milling operation practically pulverized the fibre, with the result that while the heel or sole made from the compound had a frictional resistance to slipping somewhat superior to that of rubber compound not impregnated with such material, it was far inferior to unbroken or undestroyed fibres such as found in plugs.

According to the present invention, the heel is made of a very large percentage of textile fibre with some partially cured rubber mixed therewith, the whole being united together by unmilled or colloidal latex rubber. In the process of manufacturing this heel the milling operation is entirely dispensed with, andl the libre which forms a large part of the compound, retains its yhigh frictional qualities with the result that the heel or sole made from the material has a high coefficient of friction and offers a resistance to slipping superior even to that secured by the use of inset plugs of canvas, but in addition has high elastic qualities.

- The invention consists in the heel (or sole, for wherever the word heel is used herein the word sole may be substituted without departure from t-he invention, which contemplates both,) and the method of making the heel hereinafter described.

In the accompanying drawings illustrating the heel in its various forms, and the method of--making it, Fig. 1 illustrates one block or blank of the material; Fig. 2 illustrates a washer layer or blank; Fig. 3 is a third block of the material; Fig. 4 is a detail of the mode of securing the washers in the washer layer; Fig. 5 isa detail of construction of a heel wherein no Washers are employed; Fig. 6 is a longitudinal medial section of one form of heel embodying the invention in which washers are employed; Fig. 7 is a longitudinal medial section of a second form of heel in which a washer holding layer is employed; Fig. 8 is a longitudinal medial section of a form of heel wherein the marginal portion of the heel is provided with a thick covering of milled rubber and the top and bottom are skim-coated with such rubber; and Fig. 9 is a longitudinal medial section of a fourth form of heel in which no washers are employed, and of which a detail is shown in Fig. 5.

The several forms of heel illustrated in the drawings and their method of manufacture are described as follows: The form of heel A, illustrated in Fig. 6, is made of comminuted rubber-fibre material united together by latex rubber gel and vulcanized with washers in position. The comminuted rubber-fibre material is made by comminuting old rubber boots, overshoes, tire carcasses and the like, and separating the lighter constituents (which consist largely of textile fibre) from the rubber constituents by a blowing process. These rubber-fibre particles consist for the greater part of pieces f textile fibre to which there are adherent and with'which there are' mixed small particles of partially cured rubber. The actual proportions of rubberand bre are about each. By the expression fpartially cured rubber is meant rubber vulcanized with an amount of sulphur (or its equivalent) insufiicient to transform the rubber latex.

' larger proportion of latex rubber is desired in the finished product, also it may be dispensed with in case the'surplus latex material is removed by compression or bycentrifuging.

The rubber-fibre material thus wetted is dried in layers which, when compressed, will be of the proper thickness to form biscuit -for use in manufacturing heels, and the biscuit are then used in the ordinary heel molds. The drying of the fluid rubber latex converts it into latex rubber gel. The biscuit after having been dried are compressed to compact the reticulated mass into a size suitable for use in the usual heel molds. This form of the invention contemplates the use of iron washers 2, which are placed on the washer pins in the molds, the biscuit being laid on top of the pins in the molds, and then when the molds are closed, they are subjected to heat and pressure by means of which the compound of rubber-fibre material and fluid rubber latex flows so as to lill the mold cavity and to embrace the washer pins andwashers. The heel thus produced consists of about 90% rubberfibre material united together by about 10% of vulcanized latex rubber, the excess of sulphur in the partially cured rubber adherent to or mixed with the rubber-fibre material serving to vulcanize the latex rubber gel and to form a homogeneous heel having high frictional qualities, of light weight, and durable in wear. Additional sulphur may be added if found necessary to produce the desired resiliency of finished product; it will usually be less in amount than that in the old rubber.

The vulcanized latex rubber gel of the biscuit.

after vulcanization becomes vulcanized latex y rubber.

that obtained by drying down to a gel. But

tively large as compared to the normal size rubber globule, more latex rubber is required to effect a continuous structurel throughout the mass, while, if coagulation is rapid, large string-like, tough rubber tendrils are formed in the network of which the partially 4cured rubber particles and fibre are enmeshed, but not necessarily completely surrounded as regards each particle of fibre.

In the case of the gel all of the solids in the latex, natural to it or added, are entrained and surrounded, each individually, by a film of the rubber gel. Thus all of the interstces are satisfied or filled with the rubber gel, while in the case of the coagulum the contracting reticulate network of solid latex rubber tends to express some of the non-rubber solids with the fluid latex serum.

In the heel B shown in Fig. 7, an intermediate laye of washer holding material is provided. This layer consists of a bat of cotton or other textile fibre impregnated with fluid rubber latex and dried. The material is then compressed and died out in heel form pieces or blanks, or it may be died out and then compressed, after which nail holding washers are clinched in position in the blanks. This heel is made up of three superimposed blanks 10, 11 and 12. The bottom blank 10 consists of compressed rubber-fibre material and latex rubber gel.' During compression the blank is conveniently provided with washer-pin holes to facilitate placing the blank on the washer pins in the mold cavity. The washer blank 11 is made of a latex impregnated and dried and compressed fibre bat in which the washers 13 have been set as shown in Fig. 2. The third blank l2 is the same in composition as 10. Thisblank 12 is thinner than the blank 10. The bottom blank 10 is placed in the mold cavity and pressed down therein until the washer pins project up through the washer-pin holes, then the blank 11 is placed in the mold, the washer pins engagingthe washers thereof, the top layer or blank is then inserted and the molds are closed and the heel is vulcanized in the ordinary way, with the result that the heel illustrated in Fig. 7 is thus produced. The

blank 10 forms the tread layer 14, the blank 11 forms the washer holding layer 15, and the blank 12 forms the upper layer 16. The washer holding blank is preferably made smaller in size than the other two blanks so that the edges of such blank are covered by the material of the other two layers during vulcanization.

The advantage of making a heel in this manner is clear in that the 'washers may be set in the blanks 11 by a single operation of -a washer setting press eliminating the l tedious hand operation of placing the washers on the washer pins. Furthermore, the washers will be more strongly secured in-the heel because they will be held therein by izo the fibre bat layer 11 of brous material which forms a strong anchorage for the washers.

It is within the contemplation of the invention, viewed in one aspect, that the blank 11 may be formed of the same rubber-fibre and rubber latex gel as the blanks 10 and 12, the washers being set in such material instead of a fibre bat blank. This will effect an economy of manufacture as to the placing of washers but deprives the heel of the strong anchorage of the fibre bat.

Heretofore, considerable difficulty has been experienced in uniting different layers of rubber into one rubber heel, owing to the fact that any accumulations of dust on the surface of the pieces of rubber compound greatly impair the coalescent qualities of the compound in vulcanization, such recalcitrancy to a good union often resulting in insecure union between the layers, and liability of the heel to cleave on the junctural line of the layers of compound of which it is formed. But I have found that -in manufacturing heels of rubber-fibre material which are to be united by latex rubber, the latter being a very plastic, substantially pure, gum, it readily flows about and absorbs the dust and secures a firm and excellent union between the layers so that the obj ection which heretofore obtained against the use of layers in the manufacture of rubber heels does not obtain with respect to the present heel. Another reason for the excellent union of the layers resides in the interpenetration of the fibre and latex rubber, owing to the high fluidity of the latter at the temperature of vulcanization.

This heel, therefore, is a heel made of a rubber-fibre material united by latex rubber wherein washers are secured in place preferably by a laver of fibre bat.

Thel 11681 C, Shown in Fig. 8, is like that illustrated in Fig. 6 above described, with the exception that in order to secure an exposed or outside surface of uniform color the margin or lateral edges of the heel are covered by a layer 17 of milled rubber. The milled rubber will unite perfectly with the rubberfibre latex compound during vulcanization, and present an edge having the appearance of the usual rubber heel, whereas the heel shown in Fig. 6 will exhibit spots or specks or flecks of lighter color, due to the presence in the rubber-fibre latex compound of particles of 'fibre which exhibit themselves on the edge. Besides, the form shown in Fig. 8 provides a trimming area of sufficient thickness to make the heel adapted to be used on various sizes of shoe heels. In the form of the invention shownthe complet-e heel is enveloped in milled rubber, the thickness at the side and rear being sufficient to provide for trimming and the remainder covered by a skim coating conferring the usual uniform appearance of an ordinary rubber heel. This would confer upon the new shoe to which such heel is attached a pleasing uniformity of heel color without materially detracting from its durability and its light weight and anti slipping properties, for the thin skim on the tread surface would soon wear 0H in use.

It is also within the purview of the invention to add coloring matter to the fiuid latex, either by adding water soluble dye thereto, which will dye the fibre particles, or by adding a pigmentous material, such as carbon black, to ,the fluid latex.

In the form of heel D shown in Fig. 9 n'o washers are employed, the medial layer 15 of fibre bat impregnated with fiuid rubber latex serving after drying, compression and vulcanization, as an efficient means for engaging the heads of the nails by which the heel is to be secured to the shoe heel. The fibre bat when vulcanized forms a strong layer 18 which is so thoroughly united to the layers 19 and 2O of heel compound above and below it, and so resistant to deformation by reason of its stiff, strong qualities, that it will engage and hold the nails 21 by which the heel is to be secured to the shoe heel without the use of washers. An enlarged detail showing the nail in place in such a heel appears in Fig. 5.

The rubber-fibre stock of which the heel A is formed, of which the top and bottom layers of the heels B and D are formed, and of which the body of the heel C is formed, and the method of making such stock, form the subject of another application of the present inventor, Serial No. 702,697, executed of even date herewith, to which reference may be had for a full description of such method and product.

Having thus described the invention, what is claimed is:

1. A rubber heel having top and bottom layers and an intermediate layer of rubber latex impregnated fibre bat, the whole being vulcanized into an integral heel.

2. A rubber heel consisting of top and bottom layers and an intermediate layer of rubber latex impregnated fibre bat having nail washers secured therein, the whole being vulcanized into an integral heel.

3. A rubber heel consisting of`top and bottom layers and an intermediate washer carrying layer having Washers clinched therein.

4. A rubber heel consisting of partially cured particles of rubber and particles of fibre united by interstitial vulcanized latex rubber gel provided with a superficial portion of milled rubber, the whole being vulcanized into an integral heel.

5. The method of making rubber heels which consists in making top and bottom layer blanks of particles of partially cured rubber and fibre united by latex rubber gel, an intermediate layer consisting of a fibre bat impregnated with latex rubber gel, superllO posing the 'three layers, and Vuloanizing them together under heat and pressure.

6. The method of making rubber heels which consists in making top, washer and bottom layer blanks, securing nail Washers in the .Washer blank, providing the bottom layer With Washer pin holes, superposing the three layers, placing them in the mold, and vulcanizing them under heat and pressure.

In testimony whereof I have Signed my name to this specification.

WILLIAM BURTON WESCOTT. 

